CSS“反向边界半径”在元素的边界框外以创建手机陷波设计

Question

[我正在尝试使用HTML和CSS创建看起来像手机的东西，并且我希望照相机具有类似“倒置边框半径”的东西，以便将其与框架平滑地连接。

我不能只是加大它，并用白色背景的伪元素遮盖不需要的区域，因为屏幕内容可能并不总是白色。

而且，我不能在同一个元素上使用mask-image，因为“倒边界半径”实际上会超出其边界框，因此我实际上会增加面积而不是减去（加上支撑确实很低） 。

如果可能，我想避免使用SVG。

body {
  position: relative;
  overflow: hidden;
  height: 100vh;
  margin: 0;
}

.phone {
  width: 420px;
  height: 800px;
  padding: 12px 12px 24px;
  position: absolute;
  top: 32px;
  left: 50%;
  transform: translate(-50%, 0);
  background: #000;
  box-shadow: 0 8px 32px 0 rgba(0, 0, 0, .125);
  border-radius: 16px;
}

.screen {
  height: 100%;
  overflow: hidden;
  position: relative;
  background: #FFF;
  border-radius: 8px;
}

.viewport {
  height: 100%;
  position: relative;
  overflow-x: hidden;
  overflow-y: scroll;
}

.notch {
  top: 12px;
  left: 50%;
  width: 24px;
  height: 12px;
  z-index: 10;
  position: absolute;
  transform: translate(-50%, 0);
  background: #000;
  border-bottom-left-radius: 1024px;
  border-bottom-right-radius: 1024px;
}

.camera {
  top: 0;
  left: 50%;
  width: 12px;
  border: 4px solid #33244A;
  height: 12px;
  position: absolute;
  transform: translate(-50%, -50%);
  background:  #304A58;
  border-radius: 1024px;
  box-sizing: border-box;
}

<div class="phone">
  <div class="notch">
    <div class="camera"></div>
  </div>

  <div class="screen">
    <div class="viewport"></div>
  </div>
</div>

Answer 1

有四种方法，从简单到更复杂：

• radial-gradient中添加2个伪元素。

  简单易用的解决方案。可能是我会用的那个。

• 用mask-image添加2个伪元素（与上面相同，但是支持更差）。

  在代码方面，与预览版本非常相似，但带有really bad support（支持该功能的浏览器需要前缀）。

• 将2个伪元素与border-radius，box-shadow和background: transparent相加。

  需要更多代码，但至少在Chrome Version 78.0.3904.108上看起来更平滑，所以尽管差异很小，但对您来说还是值得的。无论如何，您所能做的形状都不会像以前的替代方法那样复杂，尤其是如果您要使用椭圆而不是圆形，就像在另一个问题中一样：https://stackoverflow.com/a/59278227/3723993。

• 使用SVG。

  我认为SVG解决方案在这里不值得，但是对于更复杂的形状或动画/过渡形状来说，它将是一个不错的选择。

这里您可以查看前3个解决方案：

const notch = document.getElementById('notch');
const button = document.getElementById('button');
const xrayCheckbox = document.getElementById('xrayCheckbox');
const xrayLabel = document.getElementById('xrayLabel');
const label = document.getElementById('label');

const solutions = [{
  name: 'pseudoelements + radial-gradient',
  classes: 'notch notch-gradient'
}, {
  name: 'pseudoelements + box-shadow',
  classes: 'notch notch-shadow'
}, {
  name: 'pseudoelements + mask-image',
  classes: 'notch notch-mask'
}];

let currentSolutionIndex = 0;
let currentSolution = solutions[currentSolutionIndex];
let xRayEnabled = false;

button.onclick = () => {
  currentSolutionIndex = (currentSolutionIndex + 1) % solutions.length;
  currentSolution = solutions[currentSolutionIndex];
  
  updateLabels();
};

xrayCheckbox.onchange = () => {  
  xRayEnabled = xrayCheckbox.checked;
  
  updateLabels();
};

function updateLabels() {
  if (xRayEnabled) {
    notch.className = `${ currentSolution.classes }-xray`;
    label.innerText = `${ currentSolution.name } (X-Ray)`;
    xrayLabel.innerText = 'Disable X-Ray';
  } else {
    notch.className = currentSolution.classes;
    label.innerText = currentSolution.name;
    xrayLabel.innerText = 'Enable X-Ray';
  }
}

body {
  position: relative;
  overflow: hidden;
  height: 100vh;
  margin: 0;
}

.phone {
  width: 420px;
  height: 800px;
  padding: 12px 12px 24px;
  position: absolute;
  top: 32px;
  left: 50%;
  transform: translate(-50%, 0);
  background: #000;
  box-shadow: 0 8px 32px 0 rgba(0, 0, 0, .5);
  border-radius: 16px;
}

.screen {
  height: 100%;
  overflow: hidden;
  position: relative;
  background: #FFF;
  border-radius: 8px;
}

.viewport {
  height: 100%;
  position: relative;
  overflow-x: hidden;
  overflow-y: scroll;
}

.notch {
  top: 12px;
  left: 50%;
  width: 24px;
  height: 12px;
  z-index: 10;
  position: absolute;
  transform: translate(-50%, 0);
  background: #000;
  border-bottom-left-radius: 1024px;
  border-bottom-right-radius: 1024px;
}

.notch::before,
.notch::after {
  top: 0;
  width: 8px;
  height: 8px;
  content: "";
  position: absolute;
}

.notch-gradient-xray,
.notch-shadow-xray,
.notch-mask-xray {
  background: red;
}

/* RADIAL GRADIENT SOLUTION */

.notch-gradient::before {
  left: -6px;
  background: radial-gradient(circle at bottom left, transparent 0, transparent 70%, black 70%, black 100%);
}

.notch-gradient::after {
  right: -6px;
  background: radial-gradient(circle at bottom right, transparent 0, transparent 70%, black 70%, black 100%);
}

.notch-gradient-xray::before {
  left: -6px;
  background: green radial-gradient(circle at bottom left, transparent 0, transparent 70%, cyan 70%, cyan 100%);
}

.notch-gradient-xray::after {
  right: -6px;
  background: green radial-gradient(circle at bottom right, transparent 0, transparent 70%, cyan 70%, cyan 100%);
}

/* BOX-SHADOW SOLUTION */

.notch-shadow::before {
  left: -6px;
  background: transparent;
  border-radius: 0 8px 0 0;
  box-shadow: 0 -4px 0 0 #000;
}

.notch-shadow::after {
  right: -6px;
  background: transparent;
  border-radius: 8px 0 0 0;
  box-shadow: 0 -4px 0 0 #000;
}

.notch-shadow-xray::before {
  left: -6px;
  background: green;
  border-radius: 0 8px 0 0;
  box-shadow: 0 -4px 0 0 cyan;
}

.notch-shadow-xray::after {
  right: -6px;
  background: green;
  border-radius: 8px 0 0 0;
  box-shadow: 0 -4px 0 0 cyan;
}

/* MASK SOLUTION */

.notch-mask::before {
  left: -6px;
  background: #000;
  -webkit-mask-image: radial-gradient(circle at bottom left, transparent 0, transparent 70%, black 70%, black 100%);
}

.notch-mask::after {
  right: -6px;
  background: #000;
  -webkit-mask-image: radial-gradient(circle at bottom right, transparent 0, transparent 70%, black 70%, black 100%);
}

.notch-mask-xray::before {
  left: -6px;
  background: cyan;
  -webkit-mask-image: radial-gradient(circle at bottom left, transparent 0, transparent 70%, black 70%, black 100%);
}

.notch-mask-xray::after {
  right: -6px;
  background: cyan;
  -webkit-mask-image: radial-gradient(circle at bottom right, transparent 0, transparent 70%, black 70%, black 100%);
}

.camera {
  top: 0;
  left: 50%;
  width: 12px;
  border: 4px solid #33244A;
  height: 12px;
  position: absolute;
  transform: translate(-50%, -50%);
  background:  #304A58;
  border-radius: 1024px;
  box-sizing: border-box;
}

#button {
  font-family: monospace;
  font-size: 16px;
  padding: 8px 16px;
  margin: 32px auto 16px;
  background: transparent;
  border: 2px solid black;
  display: block;
  border-radius: 2px;
}

#xray {
  font-family: monospace;
  font-size: 16px;
  padding: 0 16px;
  text-align: center;
  display: block;
  margin: 0 0 16px;
  display: flex;
  align-items: center;
  justify-content: center;
}

#xrayCheckbox {
  margin: 0 8px 0 0;
}

#label {
  font-family: monospace;
  font-size: 16px;
  padding: 0 16px;
  text-align: center;
}

<div class="phone">
  <div id="notch" class="notch notch-gradient">
    <div class="camera"></div>
  </div>

  <div class="screen">
    <div class="viewport">
      <button id="button">Change Solution</button>
      
      <label id="xray">
        <input id="xrayCheckbox" type="checkbox" />
        <span id="xrayLabel">Enable X-Ray</span>
      </label>
      
      <div id="label">pseudoelements + radial-gradient</div>
    </div>
  </div>
</div>